There was a point when the thrust bearing diameter changed, got larger. Maybe that's what you are seeing. If it where a cut down 440 crank you wouldn't see stock (I assume 400) pistons a mile down the hole, they'd be pop ups and hitting the head.
http://440source.com/bearings.htm Had to go back and re-check the deck height math but this is correct. The piston C.H. looks to be the typical 1.813" measured from the center of the wrist pin to the top of the piston. So 3.38"/2 = 1.69" + 6.358" + 1.813" = 9.861. Then 9.980"- 9.861" =.119" below the deck which seems on par for a late '70s 400. Guess I did it wrong the first time because I would have realized there is no physical way this combination of parts would have worked with a 3.75" stroke. Always a plus to know what you actually have.
Seems like the chances of it being an original forging from 1977 are slim but whatever, it's a factory forged crank in decent enough shape.
Thanks again for the replies.
